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sicp-exercise-112.html
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<!DOCTYPE html>
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<title>SICP Exercise 1.12</title>
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SICP Exercise 1.12
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<span class="label">Date</span>
<abbr class="published" title="2013-02-24T22:30:00+09:00">
<i class="icon-calendar"></i>일 24 2월 2013
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<a href="/author/wonseok-choi.html"><i class="icon-user"></i>Wonseok Choi</a>
<span class="label">Category</span>
<a href="/category/sicp.html"><i class="icon-folder-open"></i>SICP</a>.
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<p>파스칼의 삼각형 문제이다.
문제 자체는 뭘 계산하라는 건지 좀 모호한데,
그냥 주어진 위치의 값을 결과로 내는 procedure를 만들었다.
위치는 (행, 열) 형식이다.</p>
<p>다른 사람들도 이런 식으로 생각한 것같다.</p>
<p>SICP Exercise 1.12</p>
<div class="highlight"><pre><span></span><span class="c1">;; Pascal's triangle</span>
<span class="c1">;;</span>
<span class="c1">;; notation: (row, column)</span>
<span class="c1">;;</span>
<span class="c1">;; 1 (1, 1)</span>
<span class="c1">;; 1 1 (2, 1) (2, 2)</span>
<span class="c1">;; 1 2 1 (3, 1) (3, 2) (3, 3)</span>
<span class="c1">;; ... ...</span>
<span class="p">(</span><span class="k">define </span><span class="p">(</span><span class="nf">pt</span> <span class="nv">row</span> <span class="nv">column</span><span class="p">)</span>
<span class="p">(</span><span class="k">cond </span><span class="p">((</span><span class="nb">= </span><span class="nv">column</span> <span class="mi">1</span><span class="p">)</span> <span class="mi">1</span><span class="p">)</span>
<span class="p">((</span><span class="nb">= </span><span class="nv">column</span> <span class="nv">row</span><span class="p">)</span> <span class="mi">1</span><span class="p">)</span>
<span class="p">(</span><span class="k">else </span><span class="p">(</span><span class="nb">+ </span><span class="p">(</span><span class="nf">pt</span> <span class="p">(</span><span class="nb">- </span><span class="nv">row</span> <span class="mi">1</span><span class="p">)</span> <span class="p">(</span><span class="nb">- </span><span class="nv">column</span> <span class="mi">1</span><span class="p">))</span>
<span class="p">(</span><span class="nf">pt</span> <span class="p">(</span><span class="nb">- </span><span class="nv">row</span> <span class="mi">1</span><span class="p">)</span> <span class="nv">column</span><span class="p">)))))</span>
</pre></div>
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